The present invention relates to a variable phase shifting circuit which is capable of controlling the phase of an output signal with respect to an input signal suitable for use in electronic equipment by a control voltage (or current).
Prior to the present invention, there has been known in the art a circuit to deliver an input voltage to a phase shifter of plus (+) 45 degrees and a phase shifter of minus (-) 45 degrees to deliver their outputs to two sets of differential amplifiers to which the same control voltage is supplied, thus to take out the resultant output of these differential amplifiers.
However, the drawbacks with this background art circuit are that the phase shift range is limited to 90 degrees from +45 to -45 degrees and the amplitude also varies according as the phase shift angle changes.